This invention relates to an operating mechanism for vehicles with an automatic transmission, wherein the mechanism hinders the movement of the shift lever from the park position if certain conditions are not fulfilled.
Such mechanisms are already known. Accordingly, from DE-A-3 617 256, it is known to use an operating mechanism with a blocking device which in certain positions blocks said mechanism, thereby hindering the movement of the shift lever if certain conditions are not fulfilled. This known operating mechanism either locks in a park position (P) or in a neutral position (N). The condition which has to be fulfilled in order to unlock the shift lever, in either of these two positions, is that the brake pedal must be activated. An activation of the brake pedal causes a solenoid-actuated locking pin to be moved out of its locking position whereby the shift lever can be moved freely. The disadvantage with this known mechanism is that the blocking device directly locks the shift lever and that no further activation of, for example, a button is necessary in order to unlock the shift lever in connection with activation of the brake pedal. As a consequence, when checking if the shift lever is locked or not, the force is directly transmitted via the shift lever to the locking mechanism if in the locking positions. As the shift lever has a considerable length this will result in an undesired lever effect, which implies that the locking mechanism will be subjected to large forces. This locking mechanism and the shift lever therefore have to be dimensioned with respect to relatively large forces.
A known solution do the above-mentioned problem is shown in EP-A-300 268. This operating mechanism shows a blocking device which, when being moved from said locking position, requires activation of a button at the same time that the conditions of activating the brake pedal and switching on the ignition are fulfilled. When these latter conditions are fulfilled it is possible by activation of the button to move a locking pin which is mounted adjacent to the shift lever, down into the groove of a cage which is rotatably arranged on the shift lever. The rotation of said cage is performed, at least in one direction, by means of a solenoid whose position is controlled in response to whether the brake pedal is activated. This known device, however, has several disadvantages. Amongst others, all embodiments show a cage-like blocking device which is rotatably arranged on the outside of the shift lever. This design leads to relatively large surfaces between the blocking device and the shift lever being in contact, between which surfaces movement takes place. Accordingly, this can result in a relatively large frictional resistance and the design may be rather susceptible to influence of external particles which are friction-increasing. Therefore there is a risk that such a design would not work if such a negative influence occurred which would increase the frictional resistance to a level exceeding a certain predetermined force. The risk of such a malfunction is considered to be related to the size of said surface, partly because the frictional force is directly proportional to the relation of the contacting surfaces between two elements and partly because it can be assumed that the difficulty in keeping a component protected from the influence of external particles is, to a certain extent, related to the size of the surface.
A further disadvantage is that the known device has extra means, either in the form of spring or linkage devices, between the solenoid and the blocking device.
Moreover, this known device shows a blocking device which is rotated about an axis situated solely in the vertical plane. This implies that the known solution will not be able to make use of the gravitational force for moving/rotating the locking device.
From EP-A-324 469 there is known a further operating mechanism of a similar kind. This mechanism, however, has the major disadvantage that an intermediate device is pivotally mounted between the solenoid and the blocking device, which of course increases the complexity. A further disadvantage is that the blocking device is interconnected with the shift lever in such a manner that it moves together therewith.